Fine line metallic traces have heretofore usually been made utilizing a photoresist. Simply summarized, a working substrate is coated with photoresist. Thereafter, a mask having the desired fine line metallic traces is imaged onto the photoresist. The photoresist is thereafter "developed", usually in processes that require many steps, time, and careful process control. Thereafter, there remains a working substrate having the fine line pattern outlined in the developed photoresist. This pattern can be thereafter additively plated up or subtractively etched to produce the final and desired metallic fine line traces.
Unfortunately, methods of producing fine line traces utilizing the development of photoresist are complicated in the sensitivity of the photoresist, the process control required in the development process, and the time required from placement of the photoresist to the production of the substrate having the desired fine lines.
When ordinary masks are utilized, controlling of zones of high contrast in the photoresist is a problem. Photoresist in effect integrates the light incident upon it. Where a high exposure contrast is needed to delineate a boundary between a metal line in the remainder of the work substrate, light spill or diffraction can spoil the required linear by gradual light exposure of the photoresist.
Further, photoresist requires development. This is a multi-step time consuming process requiring chemistry, temperature, and light control procedures. Development adds considerable complication to the production of the required metal lines. Failure to adhere strictly to the required control limits directly impacts yield.
Finally, where development is required, time is consumed. Periods of up to one day can be consumed in the exposure and development of a single layer containing fine metal lines.